1. Technical Field
This document relates to devices and methods for the treatment of heart conditions. For example, this document relates to devices and methods for detecting heart rotors such that effectively targeted cardiac fibrillation treatments can be provided.
2. Background Information
In the heart muscle cell, electric activation occurs from the inflow of sodium ions across the cell membrane. The maximum amplitude of the action potential is about 100 mV. The duration of the cardiac muscle impulse from the electric activation is longer than that in either nerve cell or skeletal muscle. A plateau phase follows cardiac depolarization, and thereafter repolarization takes place. Repolarization is a consequence of the outflow of potassium ions.
Associated with the electric activation of cardiac muscle cell is its mechanical contraction, which occurs a little later. An important distinction between cardiac muscle tissue and skeletal muscle is that in cardiac muscle, activation can propagate from one cell to another in any direction. As a result, the cardiac activation wave fronts can have complex non-linear shapes. Ventricular activation generally starts from the inner wall of the left ventricle and proceeds radially toward the epicardium. In the terminal part of ventricular activation, the excitation wave front proceeds more tangentially.
As described above, cardiac electric events occur on an intracellular level. Such electric signals may be potentially recorded by a mapping system that includes multiple high fidelity microelectrodes, which are inserted inside a cardiac muscle cells. However, such a system is likely to be cost prohibitive and arduous to use.
Cardiac fibrillation results from turbulent cardiac electrical activity such that normal propagation of electrical waves in the heart is disrupted to create an disorganized atrial rhythm. Cardiac fibrillation results in the formation of activation wavelets, some of which may be rotating waves or ‘rotors.’ Experiments have demonstrated that stable, self-sustained rotors can exist in the atria and that high frequency activation by such rotors results in the complex patterns of activation that characterize cardiac fibrillation. Cardiac electric rotors can be treated with ablation.